Abstract
Nuclease O of Asp. oryzae was purified and crystallized from 113.5kg of wet mycelia and 2kl of culture filtrate, by salting out with ammonium sulfate and by chromatographies on CM-Sephadex C-50 and Sephadex G-100. The purified nuclease showed α single peak with apparent sedimentation constant 2.9S in an ultracentrifuge. The molecular weight measured by short column method was 64, 000. The nuclease was completely inhibited by the specific nuclease inhibitor obtained from Asp. oryzae. The nuclease was activated by 0.1mM Mg2+ and Mn2+, and completely inhibited by 1mM EDTA. Optimum pH for activity was 7.6 for RNA and 7.4 for DNA. The nuclease degraded polyadenylic acid, polyuridylic acid and polycytidylic acid without forming detectable amount of mono-nucleotides. And, the main product from RNA was oligonucleotides. The enzyme showed no nonspecific phosphodiesterase activity.
